Apparatus for and method of introducing combustion air to a regenerative furnace



March 23, 1965 R. A. SHANNON 3,374,734,

APPARATUS FOR AND METHOD OF INTRODUCING COMBUSTION AIR TO A REGENERATIVE FURNACE Filed July 25, 196? INVENTOR ROBERT A. SHANNON A ffarney United States Patent APPARATUS FOR AND METHOD OF INTRODUQ ING CUMBUSTION Am T0 A REGENERATKVE FURNACE Robert A. Shannon, Whitehall, Pa, assignor to United States Steel (Iorporation, a corporation of New Jersey Filed July 25, 1963, Ser. Io. 297,593 2 Claims. (Cl. 263-45) The present invention relates generally to regenerative furnaces and, more particularly, to an improved apparatus for and a method of introducing combustion air into an open hearth furnace of the regenerative type.

As is well known, a conventional open hearth furnace of the regenerative type is provided with a regenerative chamber at each end which contains brick checkers for heating combustion air before it passes into the furnace. During operation of the furnace, combustion air is introduced into the heated checker of the regenerative chamher at one end of the furnace while waste gases are exhausted from the furnace to the furnace stack through the chamber at the other end of the furnace to heat the checker in the chamber. After the checker in the first chamber becomes cool, the flow of combustion air is diverted to pass through the heated checker in the second chamber and the waste gases are exhausted through the first chamber to reheat the checker therein. The flow of combustion air and waste gases is alternated in this manner at regular intervals during operation of the furnace to maintain checker heat for preheating the combustion air.

Each of the two regenerative chambers is provided with a pair of fines or ducts which are connected with the furnace stack and have valved combustion air inlets disposed between the stack and the chambers. The pairs of fines serve to alternately conduct waste gases from the chambers to the stack or combustion air from the air inlets to the chambers.

Prior to my invention, a damper was provided in each flue between the combustion air inlet and the stack so that each pair of fines could be closed off from the stack at the proper time. During normal operation of the furnace the dampers in one pair of flues were closed and the air inlets therein were open to conduct combustion air to the chamber at one end of the furnace. At the same time, the dampers in the other pair of lines were open and the air inlet closed to permit exhaust waste gases to flow to the stack from the chamber at the other end of the furnace. This arrangement was reversed at regular intervals as explained above.

The damper arrangement just described was not entirely satisfactory due to the fact that the dampers did not effectively seal off the flues from the stack when the dues were on the firing cycle conducting air to the checker. Inefficient functioning of the dampers was caused by the accumulation of Waste solids on the damper seats which were deposited by the waste gases as they passed through the does when on the exhaust cycle. This accumulation of solids prevented the dampers from seating properly when they closed. As a result, the closed dampers did not provide effective seals so that the heavy draft of the stack caused large qauntities of cold combustion air to leak past the dampers and enter the stack. The leakage of cold combustion air into the furnace stack had a detrimental effect on the stack draft and stack temperature so that furnace performance grew progressively poorer and production costs increased excessively. Leakage of the combustion air also created a deficiency of air at the firing end of the furnace so that efiicient combustion of fuel at the firing end could not be achieved.

It is, accordingly, the primary object of my invention Bflidfid Patented Mar. 23, 1955 to provide an improved apparatus for and method of introducing combustion air to a regenerative furnace, such as an open hearth furnace and the like, whereby leakage of cold combustion air into the furnace stack is effectively prevented.

This and other objects will become more apparent after referring to the folowing specification and attached drawing, in which:

In the drawing afiixed to this specification and forming part thereof, an open hearth flue embodying my invention is illustrated in longitudinal section by way of eX- ample.

Referring more particularly to the drawing, reference numeral 2 designates a flue or duct leading from an open hearth furnace stack 4 to the checkers not shown in a regenerative chamber (not shown) at one end of an open hearth furnace. An inlet pipe 6 having a shut-off valve 8 therein enters the flue between the stack and the checkers for the purpose of supplying combustion air to the flue. A pair of dampers 10 and 12 are spaced along the iiue between the inlet pipe 6 and the stack 4. Dampers 10 and 12 are conventional in structure and operation. A vent pipe 14 having a shut-off valve 16 therein is provided in the flue between the dampers 1i} and 12 venting the portion of the flue between the dampers when the dampers are closed, as will be more fully explained.

In operation, to introduce combustion air to the furnace checkers, dampers 1i and 12 are closed and valves 8 and 16 in the inlet pipe I5 and vent pipe 14, respectively, are opened and a fan (not shown) is operated to cause air to flow into the flue through the inlet pipe 6. Due to the stack draft, leakage occurs around the damper 12. Leakage of combustion air around the damper it) caused by the stack draft is prevented by the ambient air being admitted to the flue between the dampers through the vent pipe 14. This ambient air feeds the leakage to the stack around the damper i2 and thus prevents the stack draft from pulling combustion air around the damper 10.

When the furnace is reversed, valves 8 and 16 are closed and dampers 10 and 12 are opened thus permitting exhaust waste gases to flow from the checkers to the stack While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim:

1. In a regenerative furnace having a regenerative chamber, a stack, a duct connecting said chamber with said stack, and a valved air inlet means in said duct between said chamber and said stack, the improvement therewith of a pair of dampers spaced along said duct between said air inlet and said stack for selectively sealing off a portion of said duct, and a valved vent opening means in said duct between said dampers.

2. A method of introducing combustion air into a regenerative furnace having a stack, and a duct connecting said furnace and said stack which comprises the steps of first isolating a portion of said duct between said stack and said furnace by completely closing two dampers spaced along said duct, venting the isolated portion of said duct to the atmosphere, and supplying combustion air under pressure to said duct at a point between said isolated portion and said furnace.

Swindell Aug. 21, 1894 Roof Oct. 13, 1963 

1. IN A REGENERATIVE FURNACE HAVING A REGENERATIVE CHAMBER, A STACK, A DUCT CONNECTING SAID CHAMBER WITH SAID STACK, AND A VALVED AIR INLET MEANS IN SAID DUCT BETWEEN SAID CHAMBER AND SAID STACK, THE IMPROVEMENT THEREWITH OF A PAIR OF DAMPERS SPACED ALONG SAID DUCT BETWEEN SAID AIR INLET AND SAID STACK FOR SELECTIVELY SEALING OFF A PORTION OF SAID DUCT, AND A VALVED VENT OPENING MEANS IN SAID DUCT BETWEEN SAID DAMPERS. 